The tighter limits introduced by EURO3 and EURO4 regulations involve the adoption of exhaust configurations, in which the converter is located close to the manifold, in order to reduce light off time, and so to obtain lower emissions. This type of configuration introduces new problems relative to optimisation of the exhaust manifold geometry, which is no longer only linked to engine performance, but also has to guarantee the best possible operation of the exhaust gas treatment system. Critical parameters include lambda probe positioning and impingement of the gas flow, along with establishment of a flow field that corresponds to the catalytic converter intake area, as imposed by well known requests of reliability and functionality. The present work is aimed at integrated modelling and experimental optimisation of exhaust manifold geometry, with regard to oxygen sensor positioning and catalyst intake flow distribution, to find the best compromise between engine performance and exhaust emissions control.

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